Truck elevator safety mechanism



Nov. 1, 1966 c. Y. BUFORD TRUCK ELEVATOR SAFETY MECHANISM 2 Sheets-Sheetl Filed Oct. 25, 1964 lfzvQnior Y CharlesYuford 33g/ jf'i-ow, N

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S i XN Nov. l, 1966 c. Y. BUFoRD 3,282,449

TRUCK ELEVATOR SAFETY MECHANISM Filed Oct. 23, 1964 2 Sheets-Sheet 2Inventor Charles Y, Buford.

United States Patent O 3,282,449 TRUCK ELEVATUR SAFETY MECHANESM CharlesY. Buford, Elmhurst, lll., assignor to Darling 8: Company, Chicago,lli., a corporation of Illinois Fied Oct. 23, 1964, Ser. No. 405,955Claims. (Cl. 214-75) The present invention relates generally to elevatorapparatus for a vehicle and more particularly to safety mechanism forelevator apparatus of vehicles such as trailers and trucks which havethe vertical movement of a load support member controlled by a flexiblelift means.

Vehicles such as trailers and trucks which are used to carry largecontainers or pallets loaded with cargo or freight are frequentlyprovided with elevator apparatus which is adapted to move the containersor pallets from ground level to the level of the truck deck or oorduring loading or unloading operations and which use a flexible cablefor lifting or lowering the load-supporting platform. Because of theheavy loads the vehicle elevator apparatus is required to support, there-is danger of injury to the cargo and the operators in the event a liftcable or the hoist mechanism controlling the lift cable breaks. Varioustypes of safety latches and other mechanism have been devised to preventdamage to goods and personnel as a result of the lift cable parting orthe hoist mechanism to which the cable is attached breaking. Because ofthe complexity and added cost of such safety devices, there has been nowide spread adoption thereof.

It is therefore an object of the present invention to provide animproved safety means for elevator apparatus having the verticalmovement of a load support member controlled by a exible lift means.

It is a further object of the present invention to provide an improvedsafety mechanism associated with a lift cable of a vehicle elevatorapparatus which is simple in construction and reliable in operation.

A still further object of the present invention is to provide animproved truck elevator safety mechanism which can be applied toexisting elevator apparatus employing a lift cable without extensivemodification thereof.

Other objects of the present invention will be evident to those skilledin the art from the following description and claims when read inconjunction with the accompanying drawing, wherein:

FIG. 1 is a fragmentary schematic perspective view of an elevatorapparatus with the safety mechanism of the present invention operativelymounted on a truck body;

FIG` 2 is a fragmentary vertical sectional View taken along the line 2-2of FIG. 1;

FIG. 3 is a fragmentary vertical sectional view showing the safetymechanism of the present invention in retracted position;

FIG. 4 is a fragmentary horizontal sectional view taken along the line4-4 of FIG. 3; and

FIG. 5 is a fragmentary vertical sectional view showing the safetymechanism of the present invention in extended position.

Since the specific structure of the truck body and elevator assemblymounted thereon is not the subject of the present invention, only somuch of the foregoing structures are shown as is necessary to disclosethe elevator safety means which comprises the subject matter of thepresent invention.

As illustrated in FIGS. 1-5 of the drawing, the vehicle elevatorapparatus in which the principal safety mechanism of the presentinvention is embodied for purposes of illustration comprises generally aload-supporting lift gate or lift platform adapted to be disposed in ahorizontal position with the opposite inner corners thereof pivotallyconnected by suitable brackets 13, 14 with the 3,282,448 Patented Nov.l, 1966 lower ends of generally square tubular lift members 16, 17,respectively. Each of the lift members 16, 17 is slidably disposed inone of the spaced parallel generally rectangular, tubular guide means11, 12, such as lengths of slotted square steel tubing, extendingvertically from just above ground level to slightly above the top of thetruck body 15 and rigidly connected to each other by the truck body 15at the rear corner portions of the frame thereof. A longitudinal openingor slot is preferably provided in the rear walls 19, 20 of each theguide means 11, 12 to accommodate the vertical movement of the brackets13, 14 secured to the lift gate 10. The guide means 11, 12 also areprovided on the inner wall sections 21, 22 thereof with a plurality ofplunger pin-receiving means or apertures 24 which are spaced a fewinches apart starting at a point adjacent the top and extending to apoint adjacent the bottom of the guide members 11, 12.

The tubular lift members 16, 17 are adapted to be slidably suspendedwithin the spaced guide means 11, 12 by a flexible cable 18 or anequivalent exible lift means which has the opposite ends thereof securedto the lower ends of each of the lift members 16, 17 and extends aX-ially the length of the lift members 16, 17. The lift cable 18 passesover idler sheaves 23, 23 adjacent the upper end portion of each of thespaced guide means 11, 12 and is operatively connected to a hoistmechanism by sets of oppositely disposed sheaves 26, 27, as willhereinafter be described.

The vertical movement of the tubular lift members 16, 17 and in turn theraising and lowering of the lift gate 10 is controlled by raising andlowering the ends of the cable 18 through any suitable hoist mechanism,including a motor-actuated reel or a hydraulic-actuated assembly. In theform of hoist mechanism 25 illustrated in the drawing, a plurality ofoppositely disposed spaced sheaves or pulleys are employed with one setof the sheaves 26 rotatably mounted on a stationary transverse rod oraxle at one end of a hydraulic cylinder 28 and another set of sheaves 27rotatably mounted on a second transverse axle which is movable by meansof the hydraulic piston rod 29 of the hydraulic cylinder` 28. It will beevident that the lower ends of the lift cable 18 can be raised orlowered as the sheaves 27 are moved toward or away from the sheaves 26by means of the hydraulic cylinder 28. The hydraulic cylinder 28 iscontrolled by a valve control rod 33 operatively connected with a valve34 which regulates the tiow of hydraulic uid from a fluid reservoir 35through a fluid pump 36 driven by a power takeolf from the engine of thetruck. Other means, of course, can be provided for driving the Huidpump, if desired.

The safety mechanism 40 with which the present invention is primarilyconcerned coacts with lift members 16, 17 and the gruide members 11, 12to prevent relative longitudinal (i.e., vertical) movement therebetweenwhen the normal tension .on the lift cable 18 is removed for any reason,such yas breakage of the cable 18 or lfailure of any of th'e parts towhich the cable 18 is operatively connected and associated. Moreparticularly, the safety mechanism 40 comprises one or morespring-actuated plunger pins 41 slidably mounted in a guide passage 42formed in the inner wall :of the lift members 16, 17 and preferablyspaced a short distance from the lower ends thereof. A tubular sleevemember 43 is preferably secured to the inner surface of the outervertical wrall section of each of the lift members 16, 17 and supports apin-actuating means which :in the form illustrated cornprises acompression spring 45. The plunger pins 41 lare normally disposed inretracted position within the wall sections of the lift members 1d, 17whzile the elevator apparatus and calble 18 yare in operating conditionwith normal tension on the lift cable 18. However, the

pins 41 are adapted to move transversely through the guide passage 42for-med in -a wfall section of the tubular lift members 16, 17 intoengagement with plunger pinreceiving means 24 formed in a wall of theguide rnembers 11, 12 when normal tension on the lift cable 18 is lost`for any reason. Each of the plunger pins 41 has a transverse passageextending diametrically therethrough at a point preferably midwaybetween the ends thereof and through which the 'lift cable 18 can freelypass. A lint washer 44 is mounted over the outer end of the plunger pin41 Iand engages the lift cable 18. The compression spring 45 having adiameter slightly larger than the pin 41 is seated within a sleevemember 43 with the outer end of the spring 45 supported Within thesleeve member 43 and engaging outer wall of the lift members 16, 17. Theplunger pin 41 is adapted to be received Iaxially within the coils ofthe spring 45 with the washer 44 engaging the inner end of the spring45. An access opening 46 is formed in the side of tlhe lift members 16,17 opposite each of the sleeve members 43 to facilitate assembly landrepair of the safety mechanism 40.

The plunger pins 41 are preferably cylindrical in cross section and havea length slightly less than the transverse width of the tubular liftmembers 16, 17 so that the outer end Iof the pins 41 whenfin retractedposition are dispo-sed Within the sleeve members 43 with the Iinner ends'lidably supported in the guide passage 42 in the inner wall section ofthe lift members, 16, 17. The plunger pins 41 in the for-n1 illustratedpreferably have `a diameter of about 9% of an inch, a maximum sheeryload of about 22,000 lbs. and ,a safe shock load of 2,500 lbs. The sizeand strength of the pins 41 can, of course, be varied depending upon thesize of the elevator apparatus. It will be understood, however, that thedimensions of the pins 41 can vary depending upon the materials used andthe load requirements of the particular unit. v

From the foregoing description it will be evident that when there istension on the lift cable 18 either due to the weight of the lift gate10 or as a result of the pull exerted by the lhoist mechanism 25, thecable 18 is main tained in substantially vertical or axial positionwithin the lift members 16, 17. With the cable 18 disposed Iaxially inthe lift members 16, 17, the plunger pins 41 which are engaged by thecable 18 are held in a retracted position within the lift members 16, 17with the inner end of each plunger pin 41 slidably supported by la guidepassage 42 fand with the spring 45 under compression as the result ofthe cable urging the Washer 44 tnansversely toward the 4outer Wall ofthe lift members 16, 17, 4as best shown in FIG. 4 of the drawing.

When the normal tension on the cable 18 is 'lost due to the cable 18breaking or the associated hoist mechanism failing, the cable becomesslack and the compression spring 45 acting aga-inst washer 44 urges thepins 41 transversely. As the lift members 16, 17 descend within theguide means 11, 12, the plunger pins 41 will coincide with one of thesevenal vertically spaced apertures 24 formed in the inner wall sections21, 22 of the guide members 11, 12 and the plunger pins 41 will engagein the plunger pinareceiving aperture 24, whereupon the pins 41 serve asa key locking the lift members. 16, 17 and the guide means 11, 12against funther relative vertical movement and prevent further descentof the lift gate 10, as best shown in FIG. of the drawing. With aplunger pin 41 having a diameter of about 3/4 of an inch and with acompression spring 45 formed of siX coils Iof .115 inch spring Wire withan uncompressed length of 11/2 inches and a load rate of 50 pounds, ithas been found desirable to have the passages 24 in the form of ovalslots 11/2 inches long and 'Ma of an inch in diameter in order to insurethe entry of the plunger pins 41 in the lirst of tbe apertures 24 withwhich the plunger pins coincide after the lift gate 10 begins itsdescent when the lift cable 18 breaks or tension is lost in the liftcable 18 for any other reason. As soon as tension is restored to thecable 18 the pins 41 Iare returned to their normal retracted positionwithin the lift members 16, 17 and the lift igate 10 can be movedvertically in the normal operation of the elevator apparatus.

It will be understood that the optimum dimensions of the passage 24 willdepend Ion the size of the pin 41 Iand the type of spring used and ltheinvention is in no Way limited to the use of any particular part orpassage dimension.

It will be also evident that the safety mechanism 40 as above describedis adapted for use with iany elevator apparat-us employing a lift cable#for vertically moving the lift gate .and having la lift member attachedto the lift gate and operatively associated with a lixed guide means.And, While the prefer-red embodiment of the invention shows aload-supporting means and lift members supported between two spacedguide means, it is also possible to empl-oy the safety mechanism of thepresent invention in an elevator structure having a single lift membermovable vertically relative to a single fixed guide means, as in aforked lift truck apparatus.

I claim:

1. In a vehicle having in combination Aan elevated loadsupporting floor,-an elevator apparatus mounted on said vehicle and adapted to movevertically between the ground level and the level of said supportingiioor with said elevator apparatus including a load-supporting memberand at least one vertical lift member attached thereto land supportedfor vertical movement -relative to a fixed vertical guide means by aexible lift means and having power means connected 'with saidlift-supporting element w|hich is yadapted to raise yand lower said.load support member, the improvement comprising; a spring actuatedplunger pin mounted on said lift member .and engageable by said ilexiblelift means, said iiexible lift means adapted to be in engagement withsaid plunger pin intermediate the ends of said lift mean-s and hold saidplunger pin .in .retracted position while said flexible lift meansremains under normal tension and allow said plunger to extend outwardlyfrom said lift member when said flexible .lift means is with-out normaltension, and .a plurality of plunger pin receiving means formed in saidguide means with which said plunger pin is adapted to engage when saidexible lift means is without normal tension; whereby said guide meansand said lift member are locked against relative vertical movement untiltension is `restored to said flexible lift means.

2. In a vehicle having an elevated load-supporting door, an elevatorapparatus mounted on said vehicle and adapted to move vertically betweenthe ground level and the level of said supporting floor with saidelevator apparatus including a load-supporting member and at least onevertical lift member attached thereto and supported for verticalmovement relative to `a fixed vertical guide means by a lift cable xandlhaving power means connected with said cable which -is adapted to raiseand lower said loa-d support member, the improvement comprising; yaspring actuated plunger pin mounted for transverse movement lin .a guideformed in said lift member, said pin having a transverse passage throughwhich said lift cable is adapted to pass and hold said plunger pin inretracted position in said guide While said cable remains under normaltension and allow said plunger to extend outwardly through said guidewhen said cable is without normal tension, anda plunger pin receivingmeans formed in said guide means in which one end of said plunger pinengages when said cable is Without normal tension; whereby said guidemeans `and said lift member are locked against relative verticalmovement until tension is restored to said lift cable.

3. 1n a vehicle having an elevated load-supporting floor, an elevatorapparatus mounted on said vehicle and .adapted to move verticallybetween the ground level and the level of said s-upportnig floor Withsaid elevator apparatus including a load-supporting member and at leastone vertical lift member attached thereto and supported for verticalmovement relative to a xed vertical guide means by a lift cable Iandhaving power means connected with said cable which is adapted to raiseand lower said load support member, the improvement comprising; aplunger pin mounted for transverse movement relative to said lift memberin a guide formed integrally with said lift member, a spring meansmounted on said lift member 'and operatively associated with said pinnormally urging said pin transversely in sai-d guide, said plunger pinhaving -a passage extending transversely therethrough between the endsthereof through which said lift cable is adapted to ,pass and hold saidpin in retracted position in said guide while said cable remains undernormal tension and allow one end of said plunger pin to extendtransversely beyond said lift member when said cable is without normaltension, `and said guide means having plunger pin receiving means inwhich said one end of plunger pin is adapted to engage when tension isremoved from said lift cable; whereby said guide means and said liftmember are locked against relative vertical movement until tension isrestored to said li-t cable.

4. In a vehicle having an elevated load-supporting floor, an elevatorapparatus mounted on said vehicle and adapted to move vertically betweenthe ground level `and the level of said supportnig oor with saidelevator apparatus including a load-supporting member and spacedvertical lift members attached thereto and suppo-rted for verticalmovement within vertical guide means by a lift cable and having powermeans connected with said cable which is adapted to raise yand lowersaid load support member, the improvement comprising; a plunger pinmounted in a guide formed in each of said lift members for transversemovement relative to said lift mem-bers, a spring means mounted on eachof said lift members and operatively lassociated with each said pinnormally urging said pin transversely of said lift member in said guide,each said plunger ,pin having a passage extend-ing transverselytherethrough between the ends thereof:` through which said lift cable isadapted to pass and which holds said pin in retracted position in saidguide while said cable remains under normal tension and allow one end ofsaid plunger pin to extend transversely beyond `said lift member whensaid cable is without normal tension, and a plurality of plunger pinreceiving means formed at spaced points Ialong the length of said guidemeans facing said guide of `said lift member in which said one end ofsaid plunger pin is |adapted to engage when tension i-s removed fromsaid lift cable; whereby said guide means and lift members are lockedIagainst rela-tive vertical movement until tension is restored to `saidlift cable.

5. An elevator lapparatus as in claim 4, wherein said pin receivingmeans comprises elongated passages formed in said guide means having alength -at least about twice the diameter of said plunger pins.

References Cited by the Examiner UNITED STATES PATENTS 4/ 1912 Tozser 8/1962 Bartlett

1. IN A VEHICLE HAVING IN COMBINATION AN ELEVATED LOADSUPPORTING FLOOR,AN ELEVATOR APPARATUS MOUNTED ON SAID VEHICLE AND ADAPTED TO MOVEVERTICALLY BETWEEN THE GROUND LEVEL AND THE LEVEL OF SAID SUPPORTINGFLOOR WITH SAID ELEVATOR APPARATUS INCLUDING A LOAD-SUPPORTING MEMBERAND AT LEAST ONE VERTICAL LIFT MEMBER ATTACHED THERETO AND SUPPORTED FORVERTICAL MOVEMENT RELATIVE TO A FIXED VERTICAL GUIDE MEANS BY A FLEXIBLELIFT MEANS AND HAVING POWER MEANS CONNECTED WITH SAID LIFT-SUPPORTINGELEMENT WHICH IS ADAPTED TO RAISE AND LOWER SAID LOAD SUPPORT MEMBER,THE IMPROVEMENT COMPRISING; A SPRING ACTUATED PLUNGER PIN MOUNTED ONSAID LIFT MEMBER AND ENGAGEABLE BY SAID FLEXIBLE LIFT MEANS, SAIDFLEXIBLE LIFT MEANS ADAPTED TO BE IN ENGAGEMENT WITH SAID PLUNGER PININTERMEDIATE THE ENDS OF SAID LIFT MEANS AND HOLD SAID PLUNGER PIN INRETRACTED POSITION WHILE SAID FLEXIBLE LIFT MEANS REMAINS UNDER NORMALTENSION AND ALLOW SAID PLUNGER TO EXTEND OUTWARDLY FROM SAID LIFT MEMBERWHEN SAID FLEXIBLE LIFT MEANS IS WITHOUT NORMAL TENSION, AND A PLURALITYOF PLUNGER PIN RECEIVING MEANS FORMED IN SAID GUIDE MEANS WITH WHICHSAID PLUNGER PIN IS ADAPTED TO ENGAGE WHEN SAID FLEXIBLE LIFT MEANS ISWITHOUT NORMAL TENSION; WHEREBY SAID GUIDE MEANS AND SAID LIFT MEMBERARE LOCKED AGAINST RELATIVE VERTICAL MOVEMENT UNTIL TENSION IS RESTOREDTO SAID FLEXIBLE LIFT MEANS.